Action Mechanism Of Regulatory T Cell Induced By Lactobacillus Casei On Escherichia Coli Enteritis

Bacterial enteritis is a common disease among animals and humans,which can be a great danger to the health of humans and wildlife.Probiotics are the live microorganisms which when ingested in adequate amounts confer health benefits,they play an important role in the prevention and treatment of bacterial enteritis.CD4~+CD25~+Foxp3~+Treg are the major components of Treg cells,its proportion and function are closely related to the development of pathogens in the organism,especially persistent infection.How to be affected the development and function of CD4~+CD25~+Foxp3~+Treg by probiotics?what's the connection among CD4~+CD25~+Foxp3~+Treg,Th1,Th2 and Th17?What is the role of CD4~+CD25~+Foxp3~+Treg for bacterial enteritis?These problems need to be solved urgently.By analysing L.casei-induced Treg cells and the mechanism of E.coli enteritis,L.casei-mediated immune mechanisms have an important role and broad prospects.The results for the development of antimicrobial enteritis probiotics provide new ideas.Purpose:Bacterial enteritis is a common disease in animals and humans,and it poses a serious threat to animal husbandry and human health.It is a major problem in the world.Lactobacillus casei(L.casei)is a probiotic that has many clinical applications in the prevention and treatment of enteritis.The mechanism by which probiotics regulate the immune system has not yet been elucidated.The aim is studying on the mechanism of regulatory T cell induced by Lactobacillus casei regulates mouse Escherichia coli enteritis.Methods:(1)The positive rate of CD80,CD86,MHC-?,IFN-?,IL-4,IL-17a,Tregs,Smad3,NFAT2 and Stat3 were analyzed using the flow cytometry.(2)The content of IFN-?,IL-4,IL-6,TGF-?,IL-1?,TNF-?,NO and PGE were analyzed using enzyme linked immunosorbent assay.(3)The expression of T-bet,GATA-3,RoR?t and Foxp3 were analyzed using Real-time fluorescent quantitative PCR.(4)CD4~+CD25~+and CD4~+FoxP3~+cells in the mouse duodenum were analyzed using immunofluorescence test.(5)CD4~+CD25~+Foxp3~+Tregs in mesenteric lymph nodes were separated using the immunomagnetic beads,the mouse were adoptive transferred with Treg cells labeled by CFSE,the inflammatory state was evaluated through the changes of body weight,disease activity index and morphology of mice mucosa observed after HE staining.(6)The distribution of Smad3,NFAT2 and Stat3 positive cells in the mouse duodenum were analyzed using immunohistochemistry.Results:(1)L.casei regulates the differentiation and maturation of DCs,induces immune tolerance by decreasing the expression of MHC II molecules and surface costimulatory molecules on the surface of DCs in enteritis mice.(2)L.casei induces the differentiation of T cells into Th17 and Treg cells by inducing the maturation of DCs in the enteritis model mice,inducing immune responses in the body,and increasing the expression of cytokines like IL-6,IL-10 and TGF-?Treg cell differentiation and inhibiting Th17 cell differentiation.(3)L.casei increased the expression of IL-10 and TGF-?and decreased the level of IL-17a expression in the enteritis model mice.The number of Treg cells was increased and the number of Th17 cells was decreased,leading to the reduction of intestinal inflammation.Adoptive transfer of CD4~+CD25~+Tregs,undermining the proportion of Th17/Treg cell balance,promoted Treg cell differentiation and reduced the expression of IL-1?,IL-6,TNF-?,NO,PGE2 and other inflammatory mediators,which reduced intestinal inflammation in mice.(4)L.casei promotes FoxP3 transcription in Tregs cells via the Smad3 and NFAT2 signal pathways.Conclusion:L.casei can regulate the differentiation of DCs,and mature and mediate the body to produce immune response.They also promote the differentiation of Th17 and Treg cells,promote the transcription and stable expression of FoxP3 in CD4~+CD25~+Foxp3~+Tregs through the Smad3 and NFAT2 signal pathways,regulate the balance of Th17/Treg cells and reduce duodenal inflammation in mice.